Method for making bromo-chloralkanes



Patented Dec. 1, 1942 I 2,303,549 rmrno'n roa MAKING mono-canonsmrannsAmos G. Horney, East Cleveland, Ohio, assignor,

by mesne assignments, to Air Reduction Company. Incorporated, acorporation of New York No Drawing. Application April 24,1939,

Serial No. 269,793

-6Claims. (CL260-658) i This invention relates to the thesis of hyjdrocarbon compounds having the general formula of CnHa and relates moreparticularly to a new and improved process for making cyclohydrocarbons.

The present invention makes possible the production or hydrocarbons ofthe general formula, Just stated, i.- e., oleflns and cyclic compounds,irom'ncn-cyclic, substituted hydrocarbons by a new and improved process.Briefly stated, this process includes the steps of providing a suitablesubstituted alkane containing three or more carbon atoms and twodiilerent halogens selectedtuted' alk-ane is, as followsz- -Normal,propyl irom the group consisting of chlorine, bromine and a I iodineand then treating such a substituted alk'ane with zinc dust insuspension in a liquid medium,

which is preferably predominantly aqueous, in a manner to produceolefins or cyclohydrocarbons of the general formula Cama- The presentinvention will first be described with specific reference to theproduction of cyclopropane.

The production of a substituted alkane suitable for the present purposemay be accomplished by any one or several different methods.

One such method is as follows: Hydrogen bromide is passed into a halogensubstituted alkene,

such as allyl chloride, in the presence of a suitable catalyst such asparaldehyde, or while exposed to light, such as sunlight orultra-violetlight. The resulting product will containl-bromo-S-chloropropane and 2-bromo-1-chloropropane, according to thefollowing reaction:

7 CH2C1CH=CHa-l-HBr- CHaCl-CHa-CH:Br

and

' CHaCl-CHBr-CH: V

The product of the foregoing reaction may be washed with water andneutralized with an alkali,

such as sodium carbonate, dried and then distilled. Since thez-bromc-l-cholropropane boils at about 118 C.. it may be separatedreadily from the'1-bromo-3-chloropropane which hasa boiling point ofabout 142 C. and each of these substances may thus be obtained withrelatively high degrees of purity. The l-bromo 3 chloropropane,CHz-'-ClCHa-CHzBr, is a substituted alkane which maybe treated accordingto the second above mentioned step of this invention ior' conversioninto cyclopropane. The 2-bromo-1- chloropropane, CHsCl-CHBr-Cfla, is asubstituted which may be treated bythe second above mentioned step ofthe present invention =ior conversion into propene.

Another method for making a suitable s1- cohol is treated with HBr orNaBr and H2804 to yield normal propyl bromide according to the Ifollowing reaction:

' H S04 CHr-CHg-CHsOH-l-HB! -:-v CHs-CHrCHgB I-HLO This reaction productmay be washed with water and dilute alkali, dried and then purified bydistillation to separate out the normal propyl bromide. Treatment ofthis compound with chlorine gas at a pressure of about one or moreatmospheres and at a temperature of between about 25" C. and 180 C. willyield a high percentage of 1-bromo-3-chloropropane and'limited amountsof 1-bromc-2-chloropropane. Such substances may be separated andpurified as above-described in the first example and then treatedseparately according to the second above mentioned step of the presentinvention to produce respectively c'yclopropane and propene Havingprovided a suitable substituted alkane,

by the foregoing or equivalent methods, such a substituted alkane isthenvtreated according to the second above mentioned step. Whencyclopropane is the product desired, 1-bromo-3-ch1oropropane is treatedby being introduced slowly,

as by dripping it, into a liquid medium, which-is preferablypredominatingly water and which con tains zinc dust in suspension. Thisreaction mixture should be maintained at a temperature of between about70 C. and the boiling temperature of the reaction mixture which, in casesubstantially pure water is used, is 100 C. Since the reaction proceedswith greater rapidity at the higher temperatures, it is preferable tomaintain the reaction mixture at between about 90 C. and

' about 98 C.

The rate of the reaction may be increased somewhat byraising the boilingpoint of the liquid medium as may be done by adding salts thereto orincreasing the pressure.

The liquid medium may consist of water containing as much as about 20%of ethyl alcohol.

Other water-soluble, low-molecular-weight, organic compounds such asalcohols, ketones and esters may be used with water, but none of thesesubstances is necessary or desirable for they tend .to retard the rateof the reaction by lowering the boiling point.

The gases generated by the reaction are passed thru a condenser whichcondenses any water vapor but permits the gaseous cyciopropane to passtherethru. This gas has a boiling point of about -32 C. After passingthru the condenser. this to gas is collected and purified, ii necessary,by any 2 I suitable means, for example, by liquefying. distilling andscrubbing with dilute potassium pered with a liquid medium containingzinc dust in the manner above described in connection with the treatmentof the 1-bromo-3-chloropropane and the propene gas is collected asgenerated.

The foregoing description of the invention has been restricted to thepreparation of cyclopropane and propene for reasons of clarity anddefiniteness. It will be understood, however, by those skilled in theart, that the present invention may be practiced with any mixed halogensubstituted alkane containing from three to ten carbon atoms.-

For example, mixed halogen substituted alkanes .containing as many aseight or ten carbon atoms may be treated according to the presentinvention to prepare cyclohydrocarbons or alkyl substitutedcyclohydrocarbons and oleiins containing corresponding numbers of carbonatoms.

It is important that the alkanes subjected to treatment by thisinvention should contain two diiferent halogens selected from the groupconsisting of chlorine, bromine and iodine. While iodine may be used, itis preferable, for economic reasons, to use alkanes containing chlorineand bromine.

Prior to this invention dimculty has been exaaoaea'e dehyde,propionaldehyde, paraformaldehyde, benzaldehyde and nitrobenzaldehydeand a ketone such as acetone.

This reaction may be carried out under pressure as high as about 100lbs. per sq. inch and as low as about atmospheric. Where the reaction iscarried out under the higher pressure and small amounts of the foregoinginhibitors are present their inhibiting eifect in the presence of any ofthe foregoing catalysts is substantially overcome but when the reactionis carried out at about atmospheric pressure the catalysts are not aseffective.

I have found that when the allyl chloride hydrogen bromide reaction iscarried out in the presence of paraldehyde high yields ofl-bromoperienced in controlling the amounts of i-bromo- 13-chloropropane and z-bromo-i-chloropropane from the treatment of allylchloride with hydrogen bromide, i. e., the reaction was apparently notwell enough understood so that a high percentage of one compound or theother could be forecast with assurance.

.1 have discovered that high yields of l-bromo- 3-chloropropane can bemade with certainty and assurance by treating allyl chloride withhydrogen bromide in the absence of substances which inhibit the reactionor, if such substances are present, by minimizing or overcoming theirinhibiting effect by the presence of small amounts of suitable catalystsor anti-inhibitors. Freshly distilled allyl chloride does not ordinarilycontain any inhibitors and is suitable, for this reaction.

Allyl chloride which has been stored for some time in containers whichdo not include inhibitors, such as'glass, earthenware or quartzcontainers, is also suitable? for this reaction.

It is dlmcult to construct equipment, for carrying out the foregoingreaction on a commercial scale, entirely from materials which are notinhibitors of the allyl chloride hydrogen bromide reaction. Materialssuch as glass, earthenware and quartz are not inhibitors but it isdiiiicult to construct commercial equipment composed entirely of thesematerials. Equipment parts which 3-chloropropane are obtained even whenantioxidants such as hydroquinone, thio-cresol and acetic acid arepresent.

The temperature range within which hydrogen bromide will react withallyl chloride to produce good yields of 1-bromo-3-chloropropane israther wide. For example, the reaction takes place at as low atemperature as about 60 C. and proceeds quite rapidly at temperaturesbetween +7 0. and +35 C., and when the reaction temperature is betweenthe latter two temperatures and the allyl chloridehas been freshlydistilled and a suitable catalyst is present in small quantities, yieldsof as much as 85% of 1-bromo-3- chloropropane have been obtainedconsistently.

This. application is a continuation-in-part of my co-pending applicationSerial No. 200,802 iiled April 7, 1938, now Patent No. 2,219,260, issuedOctober 22. 1940. v

Having thus described the present invention so that those skilled in theart may be able to understand and practice the same, I state that what Idesire to secure by Letters Patent is delined in what is claimed.

What is claimed is:

'1. The method of making bromo-chlor-alkanes which includes the steps oftreating a substituted alkene containing three or more carbon atoms and.chlorine with hydrogen bromide in the presence of a catalyst selectedfrom the group consisting of paraldehyde, propionaldehyde,paraformaldehyde, benzaldeh'yde, nitrobenzaldehyde. i 2. The method ofmaking bromo-chlor-alkanes which includes the steps of reacting allylchloride with hydrogen bromide in the presence of a catalyst selectedfrom the group consisting of paraldehyde, propionaldehyde,paraformaldehyde, benzaldehyde,.nitrobenzaldehyde and separating the"resulting 1-bromo-3-chloropropane from other products of the reaction.

3. The method of making bromo-chlor-alkanes which includes the steps ofreacting allyl chloride with hydrogen, bromide in the presence of awould normally be used, for example, parts com- I posed of inhibitorssuch as iron, Pioneer alloy,

1 glass flber with Bakelite binding, Hastelloy Band the like may be usedto a limited extent and preterably where they do not come into contactwith the liquid. Their inhibiting-effects can be overcome by thepresence of a suitable catalyst. Suitable catalysts are simple aldehydessuch as paralsimple aldehyde and separating the resulting 1-bromo-3-chloropropane'from other products of the reaction. a

4. The method of making bromo chlor-alkanes which includes the steps ofreacting allyl chloride with hydrogen bromide in the presence of acatalyst selected from the group consisting of paraldehyde,propionaldehyde, hyde, benzaldehyde, nitrobenzaldehyde and at atemperature between about 60 C. and about +35 0. and separating theresulting i-bromo- 3-chloropropane from other products of the reaction.I

5. The method of making bromo-chlor-alkanes which includes the steps ofreacting allyl chloride 15 with hydrogen bromide inthe presence of acatparaformalde delmde. propionaldehyde,

2,803,540 f I T 3 propane which includes the steps of reacting ellyl i0.

chloride with hydrogen bromide at 's tempera-' ture between about '60 C.and about +35 C.,

at a pressure between about 100.1bs. per sq. inch and about atmospheric,and in the presence or a catalyst selected from the group consisting ofxparaldehyde, propionaldehyde per'aiormaldehyde,benz aldehyde,nitrobenzaldehyde and recovering the resulting 1-bromo-3-chloropropane.

AMOS G. HORNEY.

